Accumulation of impurities in the core of the plasma is a potential problem for any fusion reactor, and is thought to be especially problematic for stellarators. We use the collisional transport code Sfincs to calculate, in a reactor stellarator scenario, the effects of flux-surface electrostatic potential variation on tungsten transport. The potential variation is found to have a large effect on the transport, reversing the sign of the transport coefficients related to the radial electric field and the bulk ion temperature gradient, and also increasing the magnitude of the former by two orders of magnitude. We optimize the electrostatic potential variation to minimize impurity accumulation, resulting in a 20%–50% reduction of the inward impurity flux. Furthermore, we investigate whether the electrostatic potential variation caused by fast particles due to ion-cyclotron resonance heating can be used to reduce the impurity accumulation, but find the effect to be small in the cases considered.

等离子体核心中杂质的积累对于任何聚变反应堆来说都是一个潜在的问题，并且被认为对于仿星器来说尤其成问题。我们使用碰撞传输代码Sfincs在反应堆仿星器场景中，计算通量表面静电势变化对钨传输的影响。发现电位变化对传输有很大影响，反转了与径向电场和体离子温度梯度相关的传输系数的符号，并将前者的大小增加了两个数量级。我们优化静电势变化以最大限度地减少杂质积累，从而使内向杂质通量减少 20%–50%。此外，我们研究了由离子回旋共振加热引起的快速粒子引起的静电势变化是否可用于减少杂质积累，但发现在所考虑的情况下影响很小。